Degradation Detection of Power Switches in a Live Three Phase Inverter using SSTDR Signal Embedded PWM Sequence

This paper proposes a condition monitoring (CM) technique for power semiconductor devices in a live 3-phase power inverter using spread spectrum time domain reflectometry (SSTDR) embedded PWM sequence. Aging-related impedance variation within the device can be successfully characterized using SSTDR. SSTDR has been successfully used for device degradation detection in power converters while running at static condition. However, the rapid variation in impedance throughout the entire live converter circuit caused by the fast switching operation makes condition monitoring more challenging while using SSTDR. Until today, SSTDR based CM technique in a live converter requires a large amount of SSTDR data acquisition for the purpose of error reduction. The proposed method addresses this shortcoming and the experimental results validate that it requires significantly less amount of SSTDR data to successfully characterize the aging in power devices of a live three-phase inverter. Moreover, due to SSTDR’s ability to be embedded in the gate signal, the proposed technique can be integrated with the gate driver module, thus making it intelligent.